古老的石墙上布满了灰色的地衣，它们是藻类和真菌共生的产物。

The ancient stone wall was covered in gray ___lichens, a symbiotic blend of algae and fungi.

他们的爱情像地衣一样，在岁月中缓慢却坚韧地生长。

Their love grew like ___lichens, slowly but steadfastly over the years.